(i) Technical Field
The present invention relates to a folded portion flattening unit incorporated into a post-treatment device which performs various post-treatments to a sheet in which an image is formed by an image forming apparatus, the post-treatment unit, and the image forming apparatus.
(ii) Related Art
Recently, the online image forming apparatus is being promoted, and the post-treatment device for performing various post-treatments to the sheet in which the image is already formed has been widely used. Examples of the post-treatment include a stapling treatment, a bookbinding treatment, and a punching treatment.
For example, as shown in FIG. 1, an image forming apparatus 1 such as an electrophotographic printer and an electrophotographic copying machine and a post-treatment device 2 connected to the image forming apparatus 1 are well known. The post-treatment device 2 performs various post-treatments to the sheet in which the image is already formed by the image forming apparatus 1. The post-treatment device 2 includes a transport unit 3, an intermediate treatment unit 4, and a final treatment unit 5. The transport unit 3 receives the sheet from the image forming apparatus 1. The intermediate treatment unit 4 performs various intermediate treatments to the sheet taken in by the transport unit 3, and examples of the intermediate treatment include a half-folding treatment, the stapling treatment, a saddle stitching treatment, and an interposing treatment. The final treatment unit 5 performs various final treatments to the sheet delivered from the intermediate treatment unit 4. The final treatment unit 5 includes a trimming unit 6, a folded portion flattening unit 7, a punching treatment unit 8, and a stacker unit 9. The trimming unit 6 trims a sheet irregular portion at a rear end of the half-folded booklet. The folded portion flattening unit 7 flattens a curve of a folded portion at a front end of the booklet after the trimming treatment is performed. The punching treatment unit 8 performs the punching treatment near the booklet front-end portion after the flattening treatment is performed. The booklets are stacked on the stacker unit 9 after the punching treatment is performed.
When a booklet 10 which is half-folded by the intermediate treatment unit 4 is delivered to the trimming unit 6 of the final treatment unit 5 with a folded portion 10a in the lead as shown in FIG. 2A, a sheet irregular portion 10b at the rear end of the booklet 10 is trimmed by a movable blade 6a and a fixed blade 6b of a guillotine cutter which falls down toward an arrow direction as shown in FIG. 2B.